The present invention relates to antennas and more particularly to antennas capable of transmitting and receiving more than one frequency band designated by the FCC or other authority. Antennas incorporating the principles of the present invention have particular advantages for (1) simultaneous reception of 1575 MHz (GPS) signals and transmission/reception of 118-153 MHz (VHF) signals and (2) use on aircraft and other space borne vehicles.
Recent advancements in aircraft radio systems have given rise to the need for better communications in the GPS navigation and VHF data and voice communication systems. Traditionally, separate antennas were provided on aircraft designed to broadcast and receive these signals for coupling to separate on-board radio systems.
A need exists for a single antenna capable of such combination transmission for small aircraft and the like in order to minimize the use of space without detracting from the aerodynamic characteristics of the aircraft.
One antenna (commonly called the Dorne & Margolin DM CN 7-1/A) purports to provide combined GPS and VHF signal reception and includes a base plate and a whip-type VHF antenna extending rearward at a 60 degree angle from the base plate in an aerodynamically shaped housing surrounding the GPS/VHF assemblies. Means are provided for coupling both VHF and GPS signals to a common BNC connector mounted below the base plate.
Notwithstanding the purported dual transmission of GPS and VHF signals, this prior announced antenna would not be free of operational disadvantages. For example, the single BNC connector appears to be an advantage because fewer openings need be made in the aircraft skin and only one coaxial cable need be run to the connector. However, such design requires added electrical elements within the antenna itself and within the radio system to combine and then separate the various frequency signals transmitted through the single BNC connector.
Also, the internal components of the above mentioned antenna interact with and somewhat degrade the antenna transmission pattern.
Further, the leading portion of the above mentioned antenna includes a rather high profile thus reducing the aerodynamic characteristics of the antenna.